1. Field of the Invention
The present invention relates generally to an image forming apparatus and method, and in particular to an apparatus and method for image formation by scanning a photoreceptor with a plurality of interlaced scan lines.
2. Description of Related Art
As disclosed in UK Patent Application GB 2,069, 176A, an image forming apparatus for scanning with a plurality of interlaced scanning lines has been previously proposed. This system interlaces the scan lines between previously scanned lines so that the scanning lines never overlap each other but are equally spaced from one another. This equally spaced scanning is achieved by solving Eq. (1): ##EQU2## where p is the distance between adjacent scan lines, P is the distance between adjacent beams on the photoreceptor, m is an integer greater than 0 and M is the number of light sources. Such an apparatus has the disadvantage of requiring a certain number of light sources dependent on the scan spacing. For example, if it was desired to have ##EQU3## it would be required to have a system having 3 light sources. Such a system could not have ##EQU4## with 4 sources or with 2 sources. Also, this system does not allow multiple scanning, where subsequently laid down scans are scanned on top of scans previously laid down, or fractional scanning where the interlaced scan lines are unequally spaced from one another.
U.S. Pat. No. 4,445,126 discloses an image forming apparatus in which a recording medium is scanned with plural light beams. It does not disclose interlacing light beams.